Following the detailed entry evaluation, daily simplified electrophysiological tests in the form of conduction velocity and amplitude of the sural SNAP and common peroneal CMAP in one leg using surface electrode stimulation and recording electrodes will be assessed. To minimize artifacts, the same electrode site will be marked and similar size electrode will be used for each patient on a daily basis. A 25% decrease from baseline SNAP and CMAP measured at ICU admission will be taken as the minimum consistently detectable reduction.If SNAP or CMAP decreases by more than 25% on two consecutive days, a complete electrophysiological test will be performed. Complete electrophysiological testing includes nerve conduction study and electromyography.Electromyography will be recorded using a coaxial needle electrode in the tibialis anterior and first dorsal interossei.If the complete electrophysiological test is consistent with critical illness weakness, complete weekly tests will replace daily tests until ICU discharge.